The invention relates, first of all, to a process for the bonding of, in particular, lightweight fleeces by impregnating the fleece with a bonding agent, causing this bonding agent to effect bonding during a heat treatment, and winding the fleece up, and to an apparatus for performing the process.
Carded fleeces are manufactured in all kinds of thicknesses down to 10 g/m.sup.2. However, after the carding unit, these fleeces do not as yet exhibit any strength. In case thermoplastic fibers, bicomponent fibers, or the like are mixed into the fleece, the fibrous product is bonded solely by the action of heat, i.e., by heating to the fusing temperature of one of the thermoplastic fibers (see, for example, DE 3,334,787 A1). Other fleeces are bonded by means of a liquid bonding agent. The liquid bonding agent is generally pressed into the fleece in the form of foam in a nip padder. The bonding of the fleece then takes place as a chemical process by the action of heat--namely suitably on a sieve drum under a suction draft.
Especially in connection with lightweight fleeces, there is the problem at higher velocities of introducing the impregnating agent into the fleece. The fibers of the fleece experience mutual shifting in the padder, especially at feeding speeds of 90 m/min and thereabove. In order to avoid this disadvantage, the fleece could be ironed prior to impregnation, but this would cause the fleece to lose volume, which is to be avoided